The present invention relates to an endoscope to be inserted into a tubular organ including a large intestine.
When an endoscope is inserted into a tubular organ such as a large intestine through an anus, an inserted portion of the endoscope proceeds in the winding intestine through a relatively short rectum, an S-shaped sigmoid colon with a small curvature, a descending colon and a traverse colon until the inserted portion reaches to an ascending colon. Specifically, a part of the intestine between the descending colon and the traverse colon is bent at an angle that is generally sharper than the right angle, therefore it has been difficult for operators to insert the endoscope deeply in the colons.
In addition, most part of the colons is movable in a body cavity and not held to a body wall, thus the colons, specifically the sigmoid colon, are easily elongated, shortened or deformed by external force. Therefore, even if the endoscope is forcibly inserted into the colons, the colons are merely elongated by the inserted portion, and the inserted portion is not effectively advanced deeply in the colons.
In consideration of the above problems, when the inserted portion is inserted in the colons and advanced to an extent, a bendable portion of the endoscope, which is configured at a distal end of the inserted portion, is bent at a small curvature by a remote operation from the operator, and the distal end is pressed and hooked to a creased portion of an inner wall of the colon. With the distal end hooked to the crease, the inserted portion is twisted in a circumferential direction along with the inserted portion, thus the colon is turned to be partially straightened so that the inserted portion can be advanced further with respect to the colon.
Such an endoscope for a large intestine with the inserted portion and the bendable portion is generally provided with an observation window at the distal end for capturing an image of an object, which is ahead of the inserted portion. In such case, the inserted portion is often provided further with a hood that protrudes from an outer edge of the inserted portion to prevent the observation window from directly being in contact with an intestinal wall. An example of such an endoscope is disclosed in Japanese Patent Provisional Publication HEI10-248792. In recent years, there are also provided with endoscopes having observation windows and no hoods. An example of such an endoscope is disclosed in Japanese Patent Provisional Publication 2002-125915.
When an endoscope as described above is inserted into the colons and twisted to partially straighten the colon, the bendable portion hooked to the crease may slip and be unhooked from the crease unintentionally. In such case, the operator is required to repeat the hooking and twisting operations, which consume time and may be troublesome.